Solenoid assembly with included constant-current controller circuit

ABSTRACT

A constant-current controller that supplies a constant-current to a solenoid driver for use with an electromechanical device. The controller comprises a PCB containing a constant-current control circuit. The circuit comprises a GaNFET primary switch and a secondary switch. The PCB is integrated with and made a part of the solenoid driver. A standard electromechanical device may be converted to a constant-current controlled electromechanical device by exchanging the solenoid driver.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of pending U.S. patent application Ser.No. 16/406,464, filed May 8, 2019, which is a continuation-in-Part ofU.S. patent application Ser. No. 15/098,522, filed Apr. 14, 2016, nowU.S. Pat. No. 10,378,242, entitled CONSTANT-CURRENT CONTROLLER FORINDUCTIVE LOAD which claims the benefit of U.S. Provisional PatentApplication No. 62/147,478, filed Apr. 14, 2015, the contents of whichare hereby incorporated by reference in their entirety.

TECHNICAL FIELD

The present invention relates to a constant-current controller for aninductive load such as a solenoid driver. Specifically, the inventionrelates to a constant-current controller circuitry contained on aPrinted Circuit Board (PCB) that is integrated with and made a part ofthe solenoid driver of an electromechanical device. Because theconstant-current circuitry can be packaged as part of the solenoiddriver itself in accordance with the invention, upgrading anelectromechanical device to the advantages of a constant-currentcontroller is simplified. The electromechanical device may be anelectronically actuated door latch mechanism.

BACKGROUND OF THE INVENTION

Solenoids are often used as the driver to operate many types ofelectromechanical devices, such as for example electromechanical doorlatches or strikes. In the use of solenoids as drivers inelectromechanical door latches or strikes, when power is applied to thesolenoid, the solenoid is powered away from the default state to bias areturn spring. The solenoid will maintain the bias as long as power issupplied to the solenoid. Once power has been intentionally removed, orotherwise, such as through a power outage from the grid or as a resultof a fire, the solenoid returns to its default position. Depending onthe type latch or strike (fail-safe or fail-secure), the defaultposition may place the latch in a locked (fail-secure) or unlocked(fail-safe) state. In a “fail-safe” system, as long as the latch orstrike remains locked, power has to be supplied to the solenoid tomaintain stored energy in the return spring. In a “fail-secure” system,the opposite is true.

The current to pull in the plunger of the solenoid against the returnspring is referred to as the “pick” current and the current to hold theplunger against the return spring is referred to as the “hold” current.Typically, the pick current is much greater than the hold currentregardless of whether the solenoid is used in a “fail-safe” or“fail-secure” system. Power provided to the solenoid of an electriclatch or strike is most efficiently maintained if a constant current isprovided to the inductive load.

In U.S. patent application Ser. No. 15/098,522 and assigned to HanchettEntry Systems, Inc. (the “Parent Application”), a constant-currentcontroller circuitry operable to supply a constant current to aninductive load is disclosed. The circuitry includes a switching circuitcomprising a primary switch and a secondary switch. The switches aresequentially opened and closed as timed events whereby a periodiccurrent to the solenoid becomes constant when a sufficiently largeswitching frequency is implemented. The controller may be operated as apulse-width modulated controller. In one aspect of the circuitdisclosed, the primary switch is a MOSFET.

Because of the size of the MOSFET, the PCB containing the MOSFET andsupporting components is relatively large and substantially rigid, andtherefore must be mounted remote from the solenoid and typically in thehousing of the electric latch or strike remote. Thus, since thecontroller circuitry is made an integral part of the latch or strikeitself when manufactured, retrofitting of an existing electromechanicaldoor latch or strike with constant current controller circuitry isdifficult and costly.

Therefore, there exists a need for a constant-current controller circuitto be integrated with an associated solenoid so that a constant currentcontrolled solenoid may serve as a drop-in replacement for a standardsolenoid of any solenoid-driven device.

SUMMARY OF THE INVENTION

What is presented is a constant-current controller that supplies aconstant current to an inductive load. The inductive load is composed ofan inductance (L) and series resistance (R). The controller comprises aswitching circuit. The switching circuit comprises a primary switch anda secondary switch (see the schematic in FIG. 1). During a time intervalin which the primary switch is closed (t_(on)), the secondary switch isopen and the voltage across the inductive load is equal to the sourcevoltage (V_(s)). At time t_(on) until the end of a time period (T), withthe primary switch open and the secondary switch closed, zero voltsappears across the inductive load. During this interval, load currentcontinues to flow due to the stored energy in the inductance. Theperiodic current in the inductive load is dependent upon the storedenergy, the parameters of the control circuit, and the duration oft_(on).

In certain embodiments, the controller further operates as a pulse-widthmodulation (PWM) controller that causes the periodic current in theinductive load to become constant by implementing a sufficiently largeswitching frequency. As the frequency increases, the boundary currentand the peak current approach the same constant value. In certainembodiments of this controller, the inductive load can be a solenoid, DCmotor, or a magnetic actuator. In certain embodiments of thiscontroller, the primary switch may be a GaNFET and the secondary switchis a free-wheeling diode. Although not a requirement, the inductive loadcan be used to lock or unlock an electromechanical door latch orelectromechanical strike.

Also presented is constant-current controller circuit including a GaNFETas the primary switch wherein the GaNFET and its associated electroniccomponents are mounted on a PCB and wherein the PCB is integrated withand made part of a solenoid assembly.

What is also presented is a method of retrofitting a electromechanicaldevice with constant-current controller circuitry. This method comprisesthe steps a) providing a first electromechanical device without aconstant-current controller circuit wherein the first electromechanicaldevice includes a first solenoid assembly comprising a solenoid driverand a housing; b) removing the first solenoid assembly; c) providing asecond solenoid assembly comprising a solenoid driver and PCB; d)replacing the removed first solenoid assembly with the second solenoidassembly; and e) making the required feed wire connections to convertthe first electromechanical device to a second electromechanical devicehaving the constant-current controller circuit.

In one embodiment of the method, the PCB of the second solenoid assemblyis mounted to the housing adjacent the solenoid. In another embodiment,the PCB of the second solenoid assembly is wrapped around and bonded tothe solenoid.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described, by way of example, withreference to the accompanying drawings, in which:

FIG. 1 is a functional schematic of a switching circuit, in accordancewith an aspect of the present invention;

FIG. 2 is a schematic of an embodiment of a constant current PWMcontroller circuit, in accordance with an aspect of the presentinvention;

FIG. 3 is a schematic of another embodiment of a constant current PWMcontroller circuit configured for pick and hold states, in accordancewith a further aspect of the present invention;

FIG. 4 is a generalized schematic of a PCB containing a GaFNET and itssupporting electronic components in accordance with the invention;

FIGS. 5 and 5A are views of a prior art electric strike assembly;

FIGS. 6A and 6B are views of a first embodiment of a solenoid assemblywith integrated constant-current controller circuit in accordance withthe invention; and

FIGS. 7A and 7B are views of a second embodiment of a solenoid assemblywith integrated constant-current controller circuit in accordance withthe invention.

Corresponding reference characters indicate corresponding partsthroughout the several views. The exemplifications set out hereinillustrate currently preferred embodiments of the invention, and suchexemplifications are not to be construed as limiting the scope of theinvention in any manner.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A functional schematic of the switching circuit 10 that producesconstant current in an inductive load via switches controlled bypulse-width modulation (PWM) is shown in FIG. 1. There are two switches;a primary switch 12 and a secondary switch 14. When primary switch 12 isclosed, the secondary switch 14 is open. When the primary switch 12 isopen, the secondary switch 14 is closed. The series resistance (R),indicated in the circuit as resistor 18, is the sum of the coilresistance and the load resistance. Coil inductance and total circuitresistance comprise the inductive load.

When primary switch 12 is closed, source voltage (V_(s)) is appliedacross inductor (“coil”) 16 and resistor 18. However since coil 16opposes any change in current flow by producing a counter electromotiveforce (EMF) equal to the source voltage, current flow through coil 16and resistor 18 is zero at the instant the primary switch 12 is closed,i.e., (t₀). Once primary switch 12 is closed, the counter EMF begins todecay until the voltage across coil 16 and resistor 18 equals the sourcevoltage V_(s), thereby allowing a current to flow through coil 16 andresistor 18. The time interval in which primary switch 12 is closed maybe defined as t_(on).

At the beginning of the time interval when secondary switch 14 is closedand primary switch 12 is opened (i.e. from t_(on) until the end of thecycle (T)), there is no longer a source voltage Vs across coil 16. Onceagain, coil 16 opposes the change in current flow by producing apositive EMF equal to the source voltage Vs in the direction that wasthe source voltage's direction. Therefore, current continues to flowthrough coil 16 and resistor 18 without source voltage Vs being applied.From t_(on) to the end of the cycle T, current through and voltageacross coil 16 and resistor 18 decays to zero via the EMF discharged bycoil 16. As such, the current in the inductive load is dependent uponthe circuit parameters and the rate at which the switches 12 and 14 areopened and closed with respect to each other. This rate is the PWMfrequency (f).

From the above discussion, it can be understood that current flow may beheld constant by increasing the frequency in which the switches 12 and14 are opened and closed. If the primary switch 12 is closed before thecurrent decays to zero, the initial current becomes the boundarycurrent. The load current is equal to the boundary current at thebeginning and end of each period T. Non-zero boundary current increasesthe average value of the load current. As the period T is decreasedsubstantially less than the L/R time constant, wherein L/R is the ratioof coil inductance to circuit resistance, the current may be held to anyvalue between 0 and Vs/R by varying the duty ratio of primary switch 12,where the duty ratio is defined by t_(on)/T. This constant currentcontrol is especially useful since, in the example of a magnetic lock orsolenoid driver, power to the lock can be precisely controlled byvarying the duty ratio (i.e., power can be increased to resist aninstantaneous and unwanted attempt to open the door yet be reduced whilethe door is at idle). That is, for a sufficiently high frequency, thecurrent is constant and can be maintained by a PWM controller so as tobe any value between 0 and V_(s)/R.

Further in regard to the disclosure made in the Parent Application, FIG.2 depicts a constant-current controller circuit that may be used inconjunction with an electric latch or strike. It has been found thatpower to an access control device having inductive load actuator, suchas but not necessarily limited to either a magnetic lock or a solenoiddriver, is most efficiently provided if a constant current is providedto the inductive load actuator. An exemplary circuit 20 for aconstant-current PWM controller 22 is shown in FIG. 2. The circuit makesuse of a PWM controller integrated circuit 22 with current sensing usedas the feedback mechanism. The primary switch 24 is typically a MOSFET(analogous to primary switch 12 described above) while the secondaryswitch 26 (i.e. switch 14) is typically a free-wheeling diode (shown as“Dfw”).

A current transformer 28 with two single-turn primary windings 30 a and30 b and one secondary winding 32 with N-turns is used to sense the twocomponents of the load current 34 a and 34 b. Primary windings 30 a and30 b are connected in series with switches 24 and 26, respectively.Secondary winding 32 is connected to a bridge rectifier 36, burdenresistor (R_(B)) 38, and low-pass filter resistor (R_(f)) 40 andcapacitor (C_(f)) 42. It should be noted that any component having anequivalent functionality to the current transformer 28 may be installedwithin circuit 20. For example, a skilled artisan will see that thecurrent transformer 28 may be replaced with Hall-effect sensorsspecified to have similar functionality.

When primary switch 12 is on (MOSFET 24 in FIG. 2), the first currentcomponent flows through the primary winding at Terminals 3 and 4. Thiscomponent is transformed to the secondary winding 32 as:

${i_{s} = \frac{{DV}_{s}}{NR}},{0 \leq t \leq t_{on}}$

When primary switch 24 turns off, the coil current continues to flow,due to the stored energy, but is now diverted into the free-wheelingdiode 26 (i.e. secondary switch 14). This second current component nowflows through the primary winding at Terminals 1 and 2. Due to thearranged phasing of the current transformer 28, the second currentcomponent is transformed to the secondary winding 32 as:

${i_{s} = {- \frac{{DV}_{s}}{NR}}},{t_{on} \leq t \leq T}$

The secondary currents are rectified through bridge rectifier 36 toproduce a constant current through the burden resistor 38:

${i_{B} = \frac{{DV}_{s}}{NR}},{0 \leq t \leq T}$

The value of the burden resistor is calculated to produce a voltage thatis equal to the internal voltage reference, V_(r), of the integratedcircuit:

$R_{B} = \frac{{NR}\; V_{r}}{{DV}_{s}}$

Thus, the value of burden resistance 38 establishes the feedback voltageto the PWM controller 22 at V_(r). At this voltage, PWM controller 22regulates the current through the inductive load to maintain thefeedback voltage at this operating point. Thus, the value of R_(B)establishes the value of the constant current through the inductiveload.

Still further in regard to the disclosure made in the ParentApplication, FIG. 3 shows another exemplary circuit schematic 50 thatmay be suitable for use in conjunction with an electric latch or strikewhich employs a solenoid. As is recognized in the art, solenoid-drivenactuators have long been known for their power inefficiencies. Sincetheir pull-in current (pick current) is higher than the current neededto hold the solenoid plunger in place (hold current), to save energy, itis desirable for the controller to step down the current after the fixedduration of time during which the pick current has been applied.

To improve energy efficiencies, circuit 50 may use a combination ofindividual resistors in parallel to produce a collective burden resistorthat may be used to change the operating current in the solenoid. In thecase of a solenoid, two operating points are required, with the firstbeing the pull-in or pick current. This relatively large current issourced into the solenoid coil for a short time interval to engage thesolenoid. Once the solenoid has been actuated, the pick current isfollowed by a much smaller holding or hold current to maintain theposition of the solenoid plunger. In accordance with an aspect of thepresent invention, this pick and hold operation may be accomplishedusing a constant current controller by changing the value of the burdenresistor once the solenoid has engaged, as will be discussed in greaterdetail below.

In reference to FIG. 3, circuit 50 makes use of a timer integratedcircuit 52 to establish the time interval of the pull-in operation. Thetimer receives a signal through input 54 that initiates the pull-ininterval. With no signal applied, transistor 56 (Q7) is on, Pin 1 (58 a)of PWM controller 58 (U14) is pulled to ground such that PWM controller58 is disabled. As a result, no current flows through the solenoid coilconnected at terminals 34 a (+24VDC) and 34 b (OUT#2).

When input 54 is switched to logic-level HIGH, PWM controller 58 isenabled and the pick interval starts with a logic-level HIGH at the OUTpin (52 a) of timer integrated circuit 52. This output turns ontransistor 60 (Q8) and connects resistor 62 (R71) and resistor 64 (R72)in parallel. This combined resistance value establishes the value of thepull-in current. Once the pull-in interval has expired, OUT pin 52 areturns to a logic-level LOW, transistor 60 (Q8) turns off, and resistor62 (R71) is disconnected from the circuit. Resistor 64 (R72) remains asthe burden resistance and establishes the hold current of the solenoid.By way of example, if resistor 62 has a resistance of 100 ohms andresistor 64 has a resistance of 10,000 ohms and 24 V is being supplied,the pick current will be about 0.24 A (24 V/99 ohms=0.24 A) while thehold current will be about 2.4 mA (24 V/10,000 ohms=0.0024 A). In thismanner, power efficiencies may be realized as high current is appliedonly for a set, limited period of time before the circuit switches toprovide the less-demanding hold current. The above discussion withreference to FIGS. 1-3 was disclosed in the co-pending ParentApplication.

A PCB, as known in the art, is a modular platform of electroniccomponents that are interconnected to form a circuit. The structuralbase or substrate of the PCB is formed of an insulating material. Thecircuit itself is formed by a thin layer of conducting materialdeposited in a pattern on the insulating base. The necessary electroniccomponents making up the desired circuitry are then placed on thesurface of the insulating material and soldered to the depositedconducting material. Thus the overall size of the PCB is substantiallydependent upon the types of electronic components needed to form thecircuitry and the physical sizes of the electronic components. Further,while the PCB substrate may be approximately 1.5 mm thick and itselfflexible, depending on the number of electronic components soldered tothe substrate and their physical sizes, the resulting PCB may berendered relatively rigid and inflexible.

The footprint of MOSFET 24 as disclosed in the Parent Applicationmeasures approximately 4.0 mm×5.0 mm and therefore requires a relativelylarge PCB to contain it and its supporting components. The thickness ofMOSFET 24 is approximately 1.75 mm. As a result of these physicalattributes of MOSFET 24, and the layout and construction of thenecessary supporting electronic components, the size of its PCB becomesrelatively large, measuring approximately 30.0 mm×40.0 mm, and is alsorendered rigid and inflexible. Consequently, a dedicated space must beprovided remote from the electromechanical device for mounting such alarge PCB, making a retrofit of the constant-current controller circuitas disclosed in the Parent Application difficult and impractical.

The use of a Gallium Nitride FET (GaNFET) manufactured by EfficientPower Conversion Co. of El Segundo, Calif. 90245 (part no. EPC2039) as aprimary switch in place of MOSFET 24 solves the problem. The physicalsize of a GaNFET is much smaller than a MOSFET. Therefore, the size ofthe PCB needed to support the GaNFET is much smaller. Thus, the smallerphysical size of a GaNFET/PCB will enable the PCB to be mounted directlyon an associated solenoid driver.

Referring to FIG. 4, a magnified view of much smaller PCB 120 of aconstant-current control circuit containing GaNFET 124 and itssupporting electronic components is shown. The footprint of GaNFET 124measures approximately 1.35 mm×1.35 mm and is much less than thefootprint of MOSFET 24. Its thickness is also less than the thickness ofMOSFET 24, measuring approximately 0.625 mm. The result is that a muchsmaller PCB 120 may be utilized, having a length (L) of approximately24.1 mm and a width (W) of approximately 17.5 mm. Moreover, PCB 120 isrendered flexible via the use of GaNFET 124.

The use of GaNFET 124 as the primary switch in the circuit enables PCB120 to be located within the framework of the associatedelectromechanical device and integrated with the associated solenoiddriver itself, making the circuit of a prior art electromechanicaldevise easily upgraded to a constant-current controller circuit. Theupgrade may be accomplished for the most part by a simple replacement ofthe solenoid driver.

FIGS. 5 and 5A shows an example of a prior art electric strike assembly210 as disclosed in U.S. Pat. No. 8,454,063. Electric strike assembly210 utilizes two solenoid assemblies 215 and two solenoid drivers 216 ato control release of keeper(s) 270 to their unlocked state. Eachsolenoid assembly includes solenoid driver 216 a and solenoid bracket217.

With reference to FIG. 5A depicting only one side of electric strikeassembly 210, when solenoid driver 216 a is energized and solenoidplunger 272 extends, actuating components 274 interact with each otherto permit keeper 270 to move to its unlocked state. In the example of anelectric strike assembly shown, upon extension of plunger 272, releaselever 276 rotates, allowing transmission lever 278 to rotate about pivot280 which in turn releases keeper 270 for movement to its unlockedstate. Solenoid assembly 215, solenoid driver 216 a and actuatingcomponents 274 are located within housing 282 of electric strikeassembly 210.

Power for energizing solenoid driver 216 a is provided by a switch (notshown) located remote from the strike assembly 210; a feed wire (notshown) connects the switch to solenoid driver 216 a. In the exampleshown, the switch may be a button switch, a keypad, a swipe card, or thelike. If strike assembly 210 were to be configured with constant-currentcircuits 20 or 50, because of its size, the PCB (with included MOSFET24) would have to be mounted somewhere remote from electric strikeassembly 210 making conversion of strike assembly 210 toconstant-current circuit configuration difficult.

Referring to FIGS. 6A and 6B, in accordance with the invention, solenoidassembly 315, including integrated constant-current control circuit isshown. Solenoid assembly 315 includes solenoid bracket 317, solenoiddriver 316 and generally planar PCB 120. Cavity 314 of bracket 317 issized to receive solenoid driver 316. When solenoid driver 316 isenergized, plunger 372 of solenoid driver 116 interacts with actuatingcomponents (not shown) of associated electromechanical device 310 suchas an electrical latch or strike, thereby placing the latch or strike inits locked or unlocked state as known in the art. Flange 330 may extendoutward from housing and includes mounting holes 322 for mountingsolenoid assembly 315 to the associated electromechanical device 310with appropriate fasteners (not shown). With the reduced footprint ofGaNFET 124, PCB 120 may be attached with fastener 332 to solenoid driver316 and made part of solenoid assembly 315. Feed wires 326 provideelectrical connectivity to PCB 120 and to solenoid driver 316, asneeded.

Thus, an electromechanical device 210 without a constant-current controlcircuit may be readily converted to one with a constant-current controlcircuit by:

a) providing a first electromechanical device 210 without aconstant-current control circuit, wherein the first electromechanicaldevice 210 includes a first solenoid assembly 215 comprising a solenoiddriver 216 a;

b) removing the first solenoid assembly 215;

c) providing a second solenoid assembly 315 comprising a solenoid driver316 and PCB 120;

d) replacing the removed first solenoid assembly 215 with secondsolenoid assembly 315; and

e) making the required feed wire connections to convert the firstelectromechanical device 210 to a second electromechanical device 310having said constant-current control circuit.

Referring to FIGS. 7A and 7B, an alternate embodiment of a solenoidassembly 415 with an integrated constant-current controller circuit isshown. Solenoid assembly 415 includes solenoid mounting bracket 417 andsolenoid driver 416. When solenoid driver 416 is energized, plunger 472of solenoid driver 416 interacts with components (not shown) of theelectromechanical device shown schematically as 410. In the case of anelectrical latch or strike, such interaction places the associated latchor strike in its locked or unlocked state as known in the art. Tab 430may extend from mounting bracket 417 for mounting solenoid assembly 415to the associated electromechanical device by appropriate means as knownin the art. With the reduction in size of GaNFET 124, PCB 420 may beflexed into an arcuate shape as shown, assuming the general contour ofthe outer cylindrical surface of solenoid driver 416. The length (L) andcircumference (C) of solenoid driver 416 are sized to accommodate thewidth (17.53 mm) and length (24.13 mm) of PCB 420, when flexed. As shownin FIG. 7B, flexed PCB 420 may be bonded to the cylindrical surface 440of solenoid driver 416 as known in the art. A wrap 444 may then byplaced over flexed PCB 420 for protection. Feed wires (not shown)provide electrical connectivity to PCB 420 and to solenoid driver 416,as needed. With respect to the embodiment shown in FIGS. 7A and 7B, anelectromechanical device 210 without a constant-current control circuitmay be readily converted to one with a constant-current controllercircuit by:

a) providing a first electromechanical device 210 without aconstant-current controller circuit wherein the first electromechanicaldevice 210 includes a first solenoid assembly 215 comprising a solenoiddriver 216 a;

b) removing the first solenoid assembly 215;

c) providing a second solenoid assembly 415 comprising a solenoid driver416 and integrated PCB 420;

d) replacing the removed first solenoid assembly 215 with said secondsolenoid assembly 415; and

e) making the required feed wire connections to convert the firstelectromechanical device 210 to a second electromechanical device 410having the constant-current controller circuit.

Thus, solenoid assemblies 315 and 415 may be built into an“as-manufactured” electromechanical device or serve as a “drop-in”replacement for a standard solenoid used in an existingelectromechanical device thereby converting the standard circuit to aconstant-current control circuit so as to provide the increasedefficiency and power savings enjoyed by the circuit disclosed in theParent Application.

While the invention has been described by reference to various specificembodiments, it should be understood that numerous changes may be madewithin the spirit and scope of the inventive concepts described.Accordingly, it is intended that the invention not be limited to thedescribed embodiments, but will have full scope defined by the languageof the following claims.

1-6 (canceled)
 7. A method for converting a first electromechanicaldevice without a constant-current control circuit to a secondelectromechanical device with a constant-current control circuit,wherein said first electromechanical device includes a first solenoidassembly comprising a first solenoid driver, said method comprising thesteps of: a) removing said first solenoid assembly from said firstelectromechanical device; b) providing a second solenoid assemblycomprising a second solenoid driver having an integrated PCB, whereinsaid integrated PCB includes a switching circuit having a primary GaNFETswitch and a secondary switch, wherein said primary GaNFET switch andsaid secondary switch are connectable to a coil of said second solenoiddriver; d) replacing the removed said first solenoid assembly withsecond solenoid assembly; and e) making the required feed wireconnections to said second solenoid assembly to convert the firstelectromechanical device without a constant-current control circuit tosaid second electromechanical device having said constant-currentcontrol circuit.
 8. The method in accordance with claim 7 wherein saidPCB is generally planar and secured to said second solenoid driver witha fastener.
 9. The method in accordance with claim 8 wherein said PCB isarcuate in shape and secured to a cylindrical outer surface of saidsolenoid driver. 10-14 (canceled)
 15. The method in accordance withclaim 7 wherein said PCB is secured directly on said solenoid driver.16. A method for converting a first electrical strike without aconstant-current control circuit to a second electrical strike with aconstant-current control circuit, wherein said first electrical strikeincludes a first solenoid assembly comprising a first solenoid driver,said method comprising the steps of: a) removing said first solenoidassembly from said first electrical strike; b) providing a secondsolenoid assembly comprising a plunger and a second solenoid driverhaving an integrated PCB, wherein said integrated PCB includes aswitching circuit having a primary GaNFET switch and a secondary switch,wherein said primary GaNFET switch and said secondary switch areconnectable to a coil of said second solenoid driver; d) replacing theremoved said first solenoid assembly with second solenoid assembly; ande) making the required feed wire connections to said second solenoidassembly to convert the first electrical strike without aconstant-current control circuit to said second electrical strike havingsaid constant-current control circuit, wherein said plunger of saidsecond assembly is positioned to interact with actuating components ofsaid second electrical strike.
 17. The method in accordance with claim16 wherein said PCB is generally planar and secured to said secondsolenoid driver with a fastener.
 18. The method in accordance with claim17 wherein said PCB is arcuate in shape and secured to a cylindricalouter surface of said solenoid driver.
 19. The method in accordance withclaim 16 wherein said PCB is secured directly on said solenoid driver.20. A method for converting a first electrical latch without aconstant-current control circuit to a second electrical latch with aconstant-current control circuit, wherein said first electrical latchincludes a first solenoid assembly comprising a first solenoid driver,said method comprising the steps of: a) removing said first solenoidassembly from said first electrical latch; b) providing a secondsolenoid assembly comprising a plunger and a second solenoid driverhaving an integrated PCB, wherein said integrated PCB includes aswitching circuit having a primary GaNFET switch and a secondary switch,wherein said primary GaNFET switch and said secondary switch areconnectable to a coil of said second solenoid driver; d) replacing theremoved said first solenoid assembly with second solenoid assembly; ande) making the required feed wire connections to said second solenoidassembly to convert the first electrical latch without aconstant-current control circuit to said second electrical latch havingsaid constant-current control circuit, wherein said plunger of saidsecond assembly is positioned to interact with actuating components ofsaid second electrical latch.
 21. The method in accordance with claim 20wherein said PCB is generally planar and secured to said second solenoiddriver with a fastener.
 22. The method in accordance with claim 21wherein said PCB is arcuate in shape and secured to a cylindrical outersurface of said solenoid driver.
 23. The method in accordance with claim20 wherein said PCB is secured directly on said solenoid driver.